Conventionally, a solid-state imaging device includes a plurality of photoelectric conversion elements disposed corresponding to respective pixels of a captured image. Each photoelectric conversion element photoelectrically converts incident light into electric charges of an amount corresponding to the received light intensity and accumulates the electric charges in a charges storage region.
The solid-state imaging device reads out the electric charges accumulated in the charges storage region of each photoelectric conversion element using a read-out transistor and accumulates the electric charges in a floating diffusion. Subsequently, an image signal is obtained after an amplifying process by an amplifying transistor.
The amplifying transistor amplifies an image signal corresponding to the amount of electric charges accumulated in the floating diffusion (an FD voltage) and outputs the amplified image signal. Accordingly, the output of the amplifying transistor is preferred to change linearly with respect to the FD voltage in order to obtain an appropriate image signal.